One type of surface mount connector includes an insulative housing and rows of contacts mounted in the housing. The contacts have lower ends that are connected to contact pads on the upper face of a circuit board, as by soldering thereto. One way to cause the lower ends of all contacts to engage all corresponding contact pads is to precisely machine the lower ends of all contacts so they all lie in the same plane. Then the connector can be pressed down against the circuit board and solder connections made by vapor phase soldering.
One problem encountered with this approach is that the housing sometimes warps, resulting in some contacts lying close to but not against the corresponding contact pads, resulting in poor solder connections. In addition, the cost for precisely machining the lower ends of the contacts to lie in a single plane, can add expense. The upper ends of the contacts often must be resiliently deflectable downwardly to enable connection to another connector or pads of another circuit board by merely pressing them against the upper ends of the contacts. A connector that minimized the cost of connectors of the above-mentioned type and which enabled the connectors to hold a large number of contacts without danger of poor solder connections due to warping of the housing, would be value.
In accordance with one embodiment of the present invention, a connector system is provided of the type wherein a connector has contacts depending from a connector housing for pressing against contact pads of a circuit board to solder thereto, which assures reliable solder connections despite the use of a long connector housing that may warp, and which minimizes the height and cost of the connector. Each contact has a lower end that is spring-biased downwardly so the lower face of the contact lower end lies at an initial position below the housing main lower surface. The connector housing includes a plurality of spacers that depend from the housing main lower surface by less than the initial projections of the contact lower ends. Accordingly, when the connector is pressed down against a circuit board and fixed to the circuit board, the lower ends of the contacts are resiliently deflected upwardly to a level even with the spacer lower surfaces, thereby assuring that each contact firmly engages one of the contact pads on the circuit board.
Each contact includes upper and lower contact elements and a spring that biases them apart. The housing has passages with conical shoulders that engage corresponding shoulders of the upper and lower contacts to prevent the contacts from moving completely out of the passage. The lower contact element has a narrow upwardly-extending post with a slot dividing it into a pair of beams. The upper contact element has a cylindrical hole, and the beam upper ends lie in the cylindrical hole and are biased apart to make firm contact with the walls of the cylindrical hole, thereby assuring good electrical connection between the upper and lower contact elements. The spring is a helical spring that surrounds the post. By assuring that most current flows through the post instead of the helical spring, applicant avoids the high inductance that would occur if most current passed through the spring.
The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.